Manufacture of flexible abrasive products



April 3, 1956 A. L. BALL 2,740,725

MANUFACTURE OF FLEXIBLE ABRASIVE PRODUCTS Filed July 2, 1955 2 Sheets-Sheet l DVVENTOR. ALBERT L. BALL BY Maw,

ATTORNE April 3, 1956 A. L. BALL 2,740,725

MANUFACTURE OF FLEXIBLE ABRASIVE PRODUCTS Filed July 2, 1955 2 Sheets-Sheet 2 Fig 2 Fig 5' INVENTOR. ALBERT L. BALL QZMMQV ATTORNEY United States Patent MANUFACTURE OF FLEXIBLE ABRASIVE PRODUCTS Albert L. Ball, Worcester, Mass., assignor to Bay State Abrasive Products Company, Westboro, Mass., a corporation of Massachusetts Application July 2, 1953, Serial No. 365,721

Claims. (Cl. 117-20) This application relates to flexible abrasive products. It is particularly concerned with the manufacture of such products which comprise an open mesh fabric base with deposits of abrasive granules adhesively held on the exposed surfaces of the yarns of the fabric.

It is an object of the invention to provide an improved and efficient method for the production of flexible abrasive products of the character described.

Another object of the invention is to provide a method for the production of flexible abrasive products of the character described which results in more uniform and durable products.

Other objects and advantages of the present invention will be apparent from the following specification taken in conjunction with the accompanying drawing in which:

Figure 1 is a view diagrammatically illustrating apparatus by which the abrasive products of the character described may be produced according to the present invention;

Figure 2 is an enlarged, fragmentary, diagrammatic view of a portion of the apparatus shown in Figure 2;

Figure 3 is an enlarged plan view of a portion of a flexible abrasive product made in accordance with the method of the present invention, a portion of the open mesh fabric base being shown without an abrasive de' posit thereon;

Figure 4 is a sectional view taken on line 4-4 of Figure 3;

Figure 5 is an enlarged plan view of a portion of another type of open mesh fabric which may be used as a base in carrying out the process of the present invention; and

Figure 6 is a sectional view taken on line 6-6 of Figure 5.

The process of the present invention provides an improved method by which the flexible abrasive articles or products described in copending application, Serial No. 365,722 filed July 2, 1953 may be more uniformly and satisfactorily produced. An example of such an abrasive product is illustrated in Figures 3 and 4 of the present application. It comprises an open mesh fabric base having a plurality of interlaced warp yarns 11 and filling yarns 13, the entire exposed surfaces of the yarns being covered with a deposit 15 of abrasive granules. In the illustration, a part of the open mesh fabric base is exposed by removal of the abrasive deposit from portions of the yarns.

The fabric base employed in forming the flexible abrasive product is preferably woven from continuous filament yarns. Preferably, also, the fabric after weaving and before application of the abrasive deposit is coated or pre-sized with a flexible material. The yarns are thereby not only coated, but are caused to adhere at their points of interlacing so that slipping or shifting of the yarns will be substantially prevented. When the yarns of the fabric base are of the multiple filament type 2,740,725 Patented Apr. 3, 1956 they are also impregnated to a greater or less extent. Such impregnation is usually desirable as the yarns are thus rendered substantially non-absorbent and, consequently, are not penetrated by the adhesive or bond used for applying the deposit of abrasive granules thereto. Since the bond employed is preferably rather hard, rigid and brittle, the flexibility of the abrasive product is improved if the bond is not allowed to penetrate into the fabric yarns.

According to the present improved method of producing a flexible abrasive article such as is illustrated in Figure 3, an open mesh fabric web, previously pre-sized as described above, is coated with a liquid adhesive or bondiug material. Abrasive granules are then impelled or projected against both sides of the adhesive coated web while the web itself is rapidly vibrated. Following the application of the abrasive granules, the web is heated to set the adhesive and is then given a coat of a liquid sizing adhesive. Another heat treatment is thereafter provided to cure the adhesives and thereby firmly secure the abrasive granules to the exposed surfaces of the yarns of the fabric.

In Figure 1 there is diagrammatically shown an arrangement of apparatus suitable for carrying out the novel process of the present invention. The assembly includes apparatus for applying adhesive to the web before and after the deposit of abrasive granules is applied, web-vibrating apparatus, abrasiveapplying means, and driers or heaters.

In carrying out the process of the invention with the apparatus shown, the open mesh pre-sized fabric web 17 is fed from a roll 19 through an adhesive tank or vat 21 in which the yarns of the fabric receive a coating of a suitable liquid adhesive or bond. Although other adhesives may be employed, it is preferred to use a phenolic resin adhesive such as an A-stage phenol-formaldehyde liquid resin. From the adhesive tank 21 the web 17 passes between squeeze rolls 23 which are adjusted to regulate properly the amount of bond left on the fabric yarns. The mesh openings of the fabric are then unblinded, i. e. any films of adhesive which extend across the openings are broken, before abrasive granules are applied to the adhesive coated yarns. This is done by passing the adhesive coated web over a narrow, transversely extending slot from which a gas, which may conveniently be air, is ejected at high velocity. As shown, the jet of gas is formed by providing a narrow elongated opening or slot 24, which if desired may be adj usted in width by a slide or gate 25, in the upper face of a box or casing 26. The casing 26 is located beneath the plane of the web 17 but with the slot 24 closely adjacent thereto and is of such dimension transversely of the web that the slot may extend the full width of the web. Gas under pressure is admitted to the box or casing 26 through a suitable connection 27. The jet of high velocity gas emitted from the slot 24 breaks any films of adhesive that may fill mesh openings of the fabric and thus prevents clogging of the mesh openings with the abrasive which is about to be projected onto the web.

In forming a deposit of abrasive granules evenly over the surfaces of the adhesive coated yarns of the base fabric web 17, it has been found that improved results are obtained, particularly where a thick deposit is desired, if the abrasive granules are impelled or projected against both sides of the web. Accordingly, as best shown in Figure 2, abrasive granules contained in the hopper 29 above the web 17 are fed therefrom by a feed roller 31 and projected by gravity upon the upper surface of the open mesh web. Since the yarns of the web carry a wet or sticky adhesive coating, many of the granules will be captured and held, thereby to form an abrasive deposit on the upper surfaces of the yarns. Those abrasive granules which are not captured pass through the relatively large mesh openings of the fabric web. In so doing, some of the granules will adhere to the sides of the adhesive coated yarns. Much of the remainder of the abrasive fed from the hopper 29 is caught as it falls through the web 17 by the rotating propeller 33 and is forcibly thrown upwardly against the bottom of the web where a sufficient number of granules are captured by the adhesive coating on the lower surfaces of the yarns to give an abrasive coating on the latter.

It has been found that the results are further imp'roved when the web 17 is vibrated during deposition of the abrasive granules thereon. Adjacent to the abrasive application zone which comprises abrasive hoppers 29 and 39, therefore, the web passes between vertically spaced vibrating jaws 35 and 37 and is thus caused to oscillate rapidly in a vertical direction. Such vibration not only assists in causing abrasive granules which have not adhered to the adhesive coating yarns to pass through the openings in the fabric web, but also shakes ofi abrasive granules which are insecurely adhered to the yarns and thus permits other granules to be brought into contact with the adhesive on the yarns so that a well-adhered, uniform deposit of abrasive may be obtained. Abrasive granules that do not adhere to the yarn surfaces accumulate in the hopper 39 and may be withdrawn therefrom and reused.

After the application of the abrasive deposit to the adhesive coated open mesh fabric web 17, the adhesive or bond is hardened. Since the web carries an abrasive deposit on both sides, it is very desirable to avoid contact of web with any support before hardening of the adhesive. Consequently, the web is passed directly into a curing zone that may comprise a drying oven 41 which is preferably relatively short in length and is there heated without support to a temperature sulficiently high as to quickly harden or cure the adhesive to such a state that the web may be passed over the supporting roller 43 at the exit end of the oven without damage to the abrasive deposit.

Sizing adhesive is then applied to the abrasive coated web 17 by passing the web through a tank or vat 45 in which the liquid adhesive is contained. When emerging from the tank 45 the web passes between squeeze rolls 47, that preferably are covered with absorbent material to remove excess adhesive, and is then again heated by passage through a second oven 49 in which both adhesive coats are cured. At the outlet end of the oven 49 the finished abrasive product passes over the roll 51 and may be wound on a reel 53.

As previously stated, the open mesh fabric base used for forming the flexible abrasive products with which the present invention is concerned, is preferably woven from continuous filament yarns. Among the yarns of this type which may be used are organic ones such as those of rayon, nylon and other organic synthetic fibrous materials as well as inorganic ones such as glass fiber yarns. Spun yarns derived from staple fibers such as cotton, linen and wool and some types of rayon, nylon and other synthetic fibers including glass fibers are not in general suitable for making a fabric base for the abrasive products of the present invention. This is a result of the tendency of the fiber ends in spun yarns to project into and partially obstruct the mesh openings, thus making the abrasive deposit uneven and irregular.

Although a leno or gauze weave my be used in forming the open mesh fabric used as a base for the abrasive products with which the present invention is concerned, it is preferred to employ a simple plain or twill weave, open mesh fabric. Such fabrics not only are less expensive to make, but may be produced with more even surfaces than fabrics having a leno or gauze weave. In consequence, their use permits the manufacture of flex- '3 ible abrasive products having fewer surface irregularities. Excessive surface irregularity causes undesirable deep scratches on surfaces being smoothed or polished.

The fabric shown in Figures 3 and 4 illustrates plain weaving, each pick or filling yarn 13 passing over and under alternate ends or warp yarns 11 across the width of the cloth. Alternately, the picks pass over the odd and under the even warp yarns and under the odd and over the even warp yarns.

The twill weave differs principally from the plain weave in that in the former each filling yarn interlaces from two to four warp yarns and on each successive pick the filling yarn moves the design one step to the left or right, as the case may be, thus forming a diagonal pattern in the fabric. A twill fabric in which each filling yarn passes over two ends and then under two ends, repeating this sequence across the width of the fabric is known as a two and two twill. Also, since an equal number of warp and filling yarns are shown in the recurring pattern, it is classified as an "even twill. Even twills such as two and two, three and three, and four and four" twills are alike on both sides and are uniform except for the diagonal mentioned above that is characteristic of twill weaves. The diagonal pattern of open mesh fabrics with a twill weave makes them advantageous as base fabrics for abrasive articles of certain types.

Open mesh fabrics woven with either the plain weave or with an even twill weave are preferred as bases for the flexible abrasive products with which this invention is concerned. Uneven twills and fabrics having satin or sateen weaves are often undesirable since the opposite sides are different. Moreover, fabrics woven with satin or sateen weaves are unsatisfactory because of the long exposed yarns or floats which are their principal characteristic and which make an open mesh fabric of such a weave extremely flimsy. Pile fabrics or fabrics with fancy weaves are also unsatisfactory since the desired characteristics of the present abrasive products cannot be obtained with the use of such fabrics. However, fabties with doubled warp yarns may be employed in some cases with advantage. The twill fabric illustrated in Figures 5 and 6 shows how two small, closely adjacent warp yarns or ends 61 may be substituted for a single warp yarn. The two ends together are approximately equal in size to the filling yarn 63 used and each pair of warp yarns is picked as a single end. A flatter fabric of more uniform thickness may be obtained in this way. Since the doubled warp yarns 61 are treated as a single yarn the twill fabric illustrated in Figures 5 and 6 is classified as a two and two twill. Doubled warp yarns may also be used with the plain weave or with other twill weaves.

The cloth or thread count of the base fabric employed in carrying out the process of the present invention may vary over a considerable range. For many purposes, a fabric having a count of about 24 x 24, i. e. one with 24 mcsh'es per inch in each direction, is suitable. In weaving such a fabric, filling yarns equivalent in size to about 300 denier rayon yarn may be used quite satisfactorily with single warp yarns of approximately the same size or with doubled warp yarns, each of which is approximately half the size of the filling yarn. Where a flexible abrasive product of the type described herein is to be made with larger mesh, or for particularly heavy duty, coarser or heavier yarns may be used. For example, in forming a 6 x 6 base fabric, yarns ranging in denier from about 1000 to 12,000 might be employed. Of course, where the product is to be used for very fine polishing, the cloth count may be somewhat greater than 2 4 x 24 and finer yarns will be preferred for forming such an open mesh fabric base. In order topermit substantial flattening at their points of interlacing the yarns in the warp and filling of the open mesh fabric base should be only moderately twisted. Because, however, of the greater tension to which the warp yarns are subjected during weaving they may be given a greater twist than the filling yarns.

The pre-sizing or coating of the open mesh fabric base referred to above may be carried out in any desired manner. Care should be taken, however, that no substantial uneven shrinkage of the fabric takes place during pre-sizing as the mesh openings of the fabric will thereby be rendered irregular in size. Various flexible materials may be used for the pro-sizing or coating of the open mesh fabric. It is preferred, however, to use a material which is substantially insoluble in water and the non-aqueous coolants that are commonly used in abrading and polishing operations. The pre-sizing material should also be substantially insoluble in the adhesive or bond used to hold the abrasive deposit on the yarns of the fabric but must be of such character that the adhesive or bond will adhere to the material remaining on the yarns as a surface coating.

Neoprene latex has been found to be suitable as a presizing or coating material. It may be applied to the fabric by rolling, spraying or dipping and then dried in suitable manner to make the fabric ready for use in carrying out the present process. Other synthetic latices such as those manufactured and sold by the B. F. Goodn'ch Chemical Co. under the names Geon and Hycar, which are aqueous dispersions of polyvinyl resins and of butadiene-acrylonitrile copolymers, respectively may be used instead of neoprene latex and solutions or emulsions of flexible plastic materials such, for example, as polyvinyl-butyral resins, polyvinyl acetate, ethyl cellulose and the like may be also employed. As previously mentioned multiple filament yarns will be impregnated by the presizing material and the surface coating of the yarns will cement or tack the yarns together at their intersections, thus preventing the shifting of the yarns which is usually a serious problem in the handling of open mesh fabrics. Of course, suitable means must be provided for unblinding the mesh openings of the fabric after coating with the pre-sizing material to prevent the drying of films across the mesh openings. Obviously such films would interfere with the coating of all the exposed surfaces of the yarns with abrasive.

As mentioned above, the adhesive or bond employed in securing the abrasive deposit to the pre-sized yarns of the open mesh fabric base is preferably rather hard, rigid and brittle. Phenol-formaldehyde condensation product liquid resins have been found particularly suitable for use as such bonds. In addition to having the desirable properties mentioned, such resins after curing are also substantially insoluble and thus the abrasive products formed therewith may be satisfactorily used with coolants in wet abrading and polishing operations. Although liquid phenolic resins are preferred, other adhesive materials may be used. Among such usable materials are oil modified phenolic resin varnishes, oleo resin varnishes, and urea-formaldehyde condensation product resins. The choice of a bonding adhesive will, of course, primarily depend upon the properties desired in the abrasive product being manufactured and the other materials used.

The adhesive employed is preferably applied to the web at room temperature and a liquid adhesive having suitable viscosity for proper application within the normal range of such temperatures is therefore chosen. When employing the apparatus shown in Figure 1 the web 17 in passing from the adhesive vat or tank 21 is led between squeeze rolls 23. These rolls are adjusted to leave on the yarns of the web sufficient adhesive to permit the adherence of a thick, dense coat of abrasive granules over all the exposed surfaces of the yarns. In any particular case the amount of adhesive used will vary, of course, with the size of the yarns employed, the cloth count of the open mesh fabric base, and the size of the abrasive granules to be applied.

Although the mesh openings of the open mesh fabric web 17 may be cleared or unblinded after application of the bond in any one of a number of ways, excellent results have been obtained by the use of a high velocity jet of gas as described above. The velocity required in the jet will vary with the viscosity of the bonding adhesive employed and the size of the mesh openings. With thick or viscous adhesives a higher gas velocity will be required than is needed when thin or less viscous adhestves are used. Similarly, the unblinding of the mesh openings in a fabric in which the cloth count is relatively high will usually require a higher gas velocity than is required for a fabric in which the cloth count is relatively low since the adhesive or bond films extending across the mesh openings of the fabric with the smaller openings are likely to be stronger. Adjustment of the velocity of the jet or gas may be made by varying the inlet pressure to the casing 26 or by varying the width of the slot 24 by the slide 25. The velocity of the gas emitted from the slot 24 should, in any case, be regulated to that it will not be greater than required to break the films of adhesive in the meshes. Higher velocities than this may displace the film of adhesive from the yarns or damage it and thus cause irregularity in the deposit of abrasive granules.

The vibration of the open mesh fabric web during application of the abrasive granules to the adhesive coated yarn that has been found desirable in producing improved results may be carried out in any convenient manner. Satisfactory vibration has been secured by passing the web through a slot between closely spaced, vertically arranged jaws which extend transversely of the web. The jaws are driven by any suitable means (not shown) to cause the web to oscillate rapidiy in a vertical direction. The frequency of oscillation may vary and preferably is somewhat greater when fine abrasive granules are being used than when coarser granules are employed. A frequency of vibration or oscillation between about 900 and 1200 cycles per minute has been found satisfactory. The amplitude of the oscillation may also vary but a small movement, of the order of /& inch, has been found to be generally sufficient. It is important that the jaws of the vibrating apparatus be very narrow. If jaws wider than about 4 inch are used the adhesive on the web may be picked up or disturbed to such an extent that the proper or desired abrasive deposit cannot be obtained. Preferably, the jaws are approximately & inch in width. The distance between the jaws may vary. It should be great enough to permit free passage of the web but must obviously be relatively small if the web is to be properly vibrated.

The abrasive material used may be alumina, silicon carbide or any other desired kind of manufactured or natural abrasive or mixtures thereof. The amount of abrasive deposited as a coating on the yarns of the open mesh base fabric will vary with the amount of adhesive used, the yarn size, and the size of the abrasive granules. Using a base fabric with a cloth count of 24 x 24 woven from 300 denier rayon yarns, the weight of abrasive in the deposit, for grit sizes from 600 to 280 may vary between about 7.5 lbs. to 17 lbs. per ream (9 in. x 11 in., 500 sheets). Using a base fabric with a cloth count of 16 x 16 woven from 900 denier yarns, the weight of a grit abrasive deposit may be as great as 36 lbs. per ream.

The coating of abrasive granules is such as to cover the entire exposed surfaces of the yarns of the open mesh base fabric and will, of course, vary in thickness according to the amount of abrasive in the coating. For many purposes an abrasive coating of considerable thickness is desirable. Thus, as shown with the abrasive coating 15 in Figure 3, the thickness may be such as to reduce the areas of the fabric mesh openings to about one-half of their original areas, or even less. The reduction in area of the mesh openings is related not only to the thickness of the abrasive coatings on the yarns but also to the cloth count and the yarn size of the fabric base, and the size and nature of the abrasive granules used. Consequently, it will be subject to considerable variation. In some cases the abrasive coating may comprise only a substantially single layer of individual abrasive particles. For many purposes, however, the thickness of the coating is preferably such as to cause a reduction in size of the mesh openings of from about 15 to about 40 per cent. Since an open mesh structure is desired in the final abrasive product, it is important that the deposit of abrasive granules should not be so thick or so irregular as to substantially block the mesh openings.

In obtaining abrasive deposits of considerable thickness, it is preferred to use as abrasive granules irregular cemented aggregates or clusters of fine abrasive particles. The use of such clusters or aggregates not only makes it easier to obtain thick deposits of abrasive on the yarns of the base fabrics, but it also makes it possible to obtain an abrasive deposit with which fine finishes may be secured along with rapid removal of stock.

Abrasive particles may be formed into irregular bonded aggregates or clusters by any convenient method, such, for example, as that disclosed in Jackson Patent No. 2,194,472, and with any suitable bond. In the copending application referred to above there is a discussion of the factors involved in determining the suitability of a bond for the formation of abrasive aggregates or clusters to be used in flexible abrasive products of the type with which the present invention is concerned. Although the abrasive granules used in carrying out the present invention must obviously be smaller in size than the mesh openings of the base fabric on which they are to be secured, their size, whether individual particles or bonded aggregates, may vary within wide limits. The size of the abrasive particles in such aggregates may also vary and mixtures of aggregates of different sizes may be employed as well as mixtures of aggregates with indi' vidual abrasive particles.

The rate at which the abrasive particles are fed from the hopper 29 (see Figure 2) onto the adhesive coated web 17 is not particularly critical but may be controlled by the gate 30. It is desired, however, to have an excess of abrasive falling upon the web so that ample abrasive will be available for projection against the lower surface of the web by the propeller 33. The latter may be driven by any suitable means (not shown) and is equipped with vanes 34 extending outwardly therefrom which catch the particles of abrasive falling through the mesh openings of the web and forcibly project them upwardly into contact with the lower surfaces of the adhesive coated yarns forming the web. The rate of rotation of the propeller may vary with the grit size of the abrasive particles employed, such rate being preferably somewhat less with fine abrasive particles than with larger abrasive particles. The propeller will ordinarily be caused to rotate at a speed of between about 600 and 800 R. P. M.

The heating of the abrasive coated web to cure or set the adhesive is, as pointed out above, preferably carried out in an oven. The oven may be heated in any desired manner but is preferably so constructed and operated that the web is rapidly heated so as to minimize the length of the oven 41 and, consequently, the unsupported span of the web between the squeeze rolls 23 and the roller 43. It has been found convenient when using a phenol formaldehyde liquid resin adhesive to heat the oven with hot air to a temperature of about 280 F. and to sup plement the hot air heating with radiant heat supplied from suitable devices adjacent the entrance to the oven so that the temperature of the web will be quickly raised to oven temperature. It will be understood that complete cure of the adhesive bond in the oven 41 is unnecessary, it being only required that the bond be set to such a degree that the abrasive will be dislodged from the web in passing through the sizing adhesive bath in the tank 45.

The sizing adhesive or bond employed is preferably of the same type as that employed for securing the abrasive to the fabric yarns but of somewhat lower viscosity. However, other types of adhesives may be used. A discussion of the suitability of sizing adhesives for flexible abrasive products of the type with which the present invention is concerned is to be found in the copending plication referred to above. The lower viscosity of the sizing adhesive permits it to flow more readily over the irregular surface of the abrasive deposit. The amount of sizing adhesive left on the web is determined by the setting of. the squeeze rolls 47. As previously mentioned, these rolls are preferably covered with absorbent material and, therefore, remove excess adhesive, leaving on the surface of the abrasive product only a fllm of adhesive. Consequently, when the abrasive product is cured the abrasive particles, although they are securely anchored to the yarns and are well braced, will have sharp points exposed. The abrasive product will, therefore, be capable of very efiicient performance.

The sizing adhesive coating is cured in the second oven 49 by heating in any suitable manner. After the adhesive is set to such an extent that the adhesive is no longer sticky the web may, if desired, be festooned or otherwise manipulated in the oven to permit longer heating or the use of higher or lower temperatures to complete the cure of the adhesives. The curing conditions, such as the temperature and time of heating, required to obtain the desired characteristic will, of course, vary with the adhesives employed and the intended use of the product. The choice of suitable conditions is, therefore, a matter for determination in accordance with circumstances. It will be understood that, if desired, the final curing may be carried out in apparatus other than the oven 49 and in accordance with known practice and procedures used in curing other abrasive coated articles.

By the method set forth herein flexible abrasive products of the type described in the copending application mentioned above, and filed concurrently herewith by the present applicant together with Orello S. Buckner and Philip C. Tucker, may be made more efficiently and with greater uniformity. As previously mentioned, vibration of the web assists in the passage through the mesh openings of unattached or loosely attached abrasive granules. It also assists in the wetting of the abrasive granules by the adhesive. Projection of the granules against the web is helpful in obtaining good contact between the granules and the adhesive. The process may be carried out with inexpensive apparatus and with a minimum of hand labor.

It will be understood that the invention as described is subject to modification without departing from the spirit of the invention. Thus, for example, the apparatus shown and described may be changed in many details or equivalent apparatus may be used. So, also, for example may there be changes in the open mesh fabric web employed. Thus instead of being woven of multiple filameat yarns, it may be formed from yarns each of which comprises only a single filament. Furthermore, the fabric base used may be woven of yarns precoated with a flexible, heat-softcnable material or of heat-softenable yarns as set forth in applicants copending application, Serial Number 365,641, filed concurrently herewith. Accordingly, the invention is not to be considered as limited by the specific details set forth herein, but it is to be interpreted as broadly as permitted by the appended claims.

I claim:

l. The process of manufacturing a flexible, open mesh, abrasive coated fabric having substantially unblocked mesh openings which comprises applying a hardenable adhesive to a web, said web being formed of a woven, open mesh fabric and said adhesive being applied evenly to said web in such a quantity as to provide an adhesive coating over the entire exposed surfaces of the yarns thereof; passing said web substantially horizontally through an abrasive application zone; providing, within said zone, a

substantially uniform deposit of abrasive granules on the adhesive coated surfaces of said yarns by projecting abrasive granules smaller than the mesh openings of said web against both sides of said web, an excess of abrasive granules being applied to the upper face of said web, while said adhesive is still wet and while vibrating said web in a direction normal to the plane of said web solely at a point preceding said zone, vibration of said web serving to assist passage therethrough of abrasive granules that are unattached to said adhesive coated yarns and to displace from said web abrasive granules that are insecurely adhered to said yarns; and thereafter passing said web through a curing zone in which said adhesive is hardened, said web being unsupported from a point in advance of. the point at which vibration is applied thereto to a point following said curing zone and being maintained out of contact with any portion of the apparatus used from a point preceding said abrasive application zone to a point following said curing zone.

2. A process according to claim 1 in which said fabric is Woven from continuous filament yarns.

3. A process according to claim 1 in which at least a portion of said abrasive granules are aggregates which comprise a plurality of bonded abrasive particles.

4. A process according to claim 1 in which adhesive is again applied to said web after passage through said curing zone and said adhesive is subsequently cured.

5. The process of manufacturing a flexible, open mesh, abrasive coated fabric having substantially unblocked mesh openings which comprises applying a heat hardenable adhesive to a web, said web being formed of an open mesh fabric woven from continuous filament yarns and said adhesive being applied evenly to said Web in such quantity as to provide an adhesive coating over the entire exposed surfaces of the yarns thereof; passing said web substantially horizontally through an abrasive application zone and therein forming on the adhesive coated surfaces of said yarns a substantially uniform deposit of abrasive granules, said deposit being produced while said adhesive is still sticky and while vibrating said web in a direction normal to the plane thereof solely at a point preceding said zone, by projecting against the upper face of said web an excess of abrasive granules of smaller size than the mesh opening of said fabric and projecting against the lower face of said web at least a portion of the abrasive granules passing through the mesh openings of said fabric web, vibration of said web serving to assist passage thercthrough of abrasive granules that are unattached to said adhesive coated yarns and to displace from said web abrasive granules that are insecurely adhered to said yarns; thereafter passing said web through a heated curing zone in which said adhesive is hardened. the uniformity of the abrasive deposit on said web being maintained by suspending said web unsupported from a point in advance of the point at which vibration is applied thereto to a point following said curing zone and maintaining said web out of contact with any portion of the apparatus used from a point preceding said abrasive application zone to a point following said curing zone; and subsequently applying a second coating of adhesive to said abrasive coated yarns of said web and curing said adhesive.

References Cited in the file of this patent UNITED STATES PATENTS 1,857,340 Wyatt May 10, 1932 1,883,535 Burnett Oct. 18, 1932 1,965,703 Hyde July 10, 1934 2,123,581 Anderson July 12, 1938 2,138,882 Robie Dec. 6, 1938 2,196,655 Borghetty Apr. 9, 1940 2,355,635 Dubilier Aug. 15, 1944 2,371,605 Carlton et al. Mar. 20, 1945 2,375,813 Oglesby May 15, 1945 2,388,999 Riggenbach Nov. 13, 1945 2,425,236 Ferrante Aug. 5, 1947 2,447,374 Smyser Aug. 17, 1948 2,615,477 Crawley Oct. 28, 1952 2,655,895 Abeles 1 Oct. 20, 1953 2,696,445 Schwartz et al. Dec. 7, 1954 2,696,847 Cotterill et a1. Dec. 14, 1954 

1. THE PROCESS OF MANUFACTURING A FLEXIBLE, OPEN MESH, ABRASIVE COATED FABRIC HAVING SUBSTANTIALLY UNBLOCKED MESH OPENINGS WHICH COMPRISES APPLYING A HARDENABLE ADHESIVE TO A WEB, SAID WEB BEING FORMED OF A WOVEN, OPEN MESH FABRIC AND SAID ADHESIVE BEING APPLIED EVENLY TO SAID WEB IN SUCH A QUANTITY AS TO PROVIDE AN ADHESIVE COATING OVER THE ENTIRE EXPOSED SURFACES OF THE YARNS THEREOF; PASSING SAID WEB SUBSTANTIALLY HORIZONTALLY THROUGH AN ABRASIVE APPLICATION ZONE; PROVIDING, WITHIN SAID ZONE, A SUBSTANTIALLY UNIFORM DEPOSIT OF ABRASIVE GRANULES ON THE ADHESIVE COATED SURFACES OF SAID YARNS BY PROJECTING ABRASIVE GRANULES SMALLER THAN THE MESH OPENINIGS OF SAID WEB AGAINST BOTH SIDES OF SAID WEB, AND EXCESS OF ABRASIVE GRANULES BEING APPLIED TO THE UPPER FACE OF SAID WEB, WHILE SAID ADHESIVE IS STILL WET AND WHILE VIBRATING SAID WEB IN A DIRECTION NORMAL TO THE PLANE OF SAID WEB SOLELY AT A POINT PRECEDING SAID ZONE, VIBRATION OF SAID WEB SERVING TO ASSIST PASSAGE THERETHROUGH OF ABRASIVE GRANULES THAT ARE UNATTACHED TO SAID ADHESIVE COATED YARNS AND TO DISPLACE FROM SAID WEB ABRASIVE GRANULES THAT ARE INSECURELY ADHERED TO SAID YARNS; AND THEREAFTER PASSING SAID WEB THROUGH A CURING ZONE IN WHICH SAID ADHESIVE IS HARDENED, SAID WEB BEING UNSUPPORTED FROM A POINT IN ADVANCE OF THE POINT AT WHICH VIBRATION IS APPLIED THERETO TO A POINT FOLLOWING SAID CURING ZONE AND BEING MAINTAINED OUT OF CONTACT WITH ANY PORTION OF THE APPARATUS USED FROM A POINT PRECEEDING SAID ABRASIVE APPLICATION ZONE TO A POINT FOLLOWING SAID CURING ZONE. 